Substantial Progress towards 12 GeV
Substantial Progress towards 12 GeV
December 5, 2014
Over the course of 2014, we have had several reasons to mention the CEBAF 12 GeV Upgrade Project and the resumption of beam operations, and, indeed, they have been included in several of this year’s Montage articles. However, we have not given it the lead role thus far; the intent of this article is to remedy that situation.
A year ago, we were commissioning the new cryogenic plant. We took steps to be careful with the new modes of operation and even backed off a little from our haste to get to beam commissioning in order to ensure a level of safety. The changes we made were successful, both in terms of safety and in terms of achievement. As a result, we were able to commence 2014 with a more or less immediate push on the commissioning of the accelerator.
The accelerator commissioning itself was underpinned with a rather thorough Accelerator Readiness Review process. The process was designed to ensure safety in the tricky transition period between “off” and “operational”. Our team recognized that knowing that everything is in place and is working is the key also to functionality. The tools that were developed to ensure safety formed the basis for the pre-beam commissioning. With the cooperation of our Accelerator Readiness Review team, the members of which were drawn from a number of laboratories in the DOE complex, and of our Thomas Jefferson Site Office colleagues, a phased plan was developed. If you like, we took baby steps first; walked before we ran. Thus, by February, we were able to send the beam completely around the accelerator, and in this single pass, we achieved 2.2 GeV of acceleration. This was a key performance parameter and prerequisite for an eventual 12 GeV machine.
Looking ahead to bringing the experiments into play in Hall D and Hall A, the second phase of the ARR was to look at our Experimental Readiness Review process. Again, a proactive approach was adopted by the experimental nuclear physics team. A new process, homogenized across all halls, was put in place. This then enabled the achievement of electron scattering with 3-pass CW beam with energy slightly in excess of 6 GeV into Hall A. The elastically scattered electrons were measured using one of the Hall A spectrometers. As a culmination of the spring running, 5.5 pass beam with 10.5 GeV was transported to the Hall D electron tagger dump.
Based on these successes and the completion of the accelerator scope for the project, an Energy Sciences Acquisition Advisory Board recommended the award of CD-4A, “ready for accelerator operations”, on July 30, five months ahead of schedule.
However, not everything within the project was so rosy. We were disappointed with the progress logged on several of the seven superconducting magnets being constructed for the new experimental apparatus in the halls. In a couple of cases, technical setbacks demanded remedial action; in others, the progress was steady but substantially slower than we hoped.
During the past couple of months, the situation appears to be changing. We expect the first Hall C magnet, Q1, to leave England by ship on December 18. The second magnet, coming from NSCL at Michigan State University, has had its vessel closed in the past week and should be here by spring 2015. The large dipole coils being fabricated in France have completed winding and by the time you read this article, the Q2 quadrupole coil winding will also be complete. Potting of the dipole coils is in progress. The Hall B TORUS coils are being fabricated at Fermilab, and the first was delivered and checked out before Thanksgiving. The assembly of the coils into their cryostats, and eventually into a TORUS magnet, will happen here at Jefferson Lab initially in the Test Lab and then Hall B. The solenoid practice coil, fabricated in Pennsylvania, is undergoing detailed examination as I write, so I will not attempt to characterize the status. Predicting the past is difficult, predicting the future is nigh impossible!
The status of the project was given thorough reviews – two, in fact. One was commissioned as a JSA Director’s Review and chaired by Ed Temple. The second was the DOE version, the Office of Project Assessment review. Both reviews recognized the progress we had made. However, both reviews were also concerned with our progress against the schedule and with the cost we have incurred. By this stage of the project, the dollar value remaining is a fraction of the total cost of the project. But that puts a premium on our care for these precious resources, time and money. Indeed, there was considerable emphasis on the need to treat this phase of the project, the end game, quite differently than the earlier stages. One analogy used was that in the red zone, a football game changes; with a small space in which to deploy the receivers, extra precision is required. We cannot afford the luxury of spending time on leisurely R&D; we need to be taking decisions with care but with alacrity. We need to look for ways to substantially strengthen our cost and schedule performance so as to ensure successful completion of the project.
In the meantime, the fall campaign, to take the next steps in commissioning the accelerator and experiments, bore fruit. The electron beam was delivered to the Hall D tagger, and a photon beam was created and transported into Hall D. Having been trained with cosmic rays, the GlueX experiment saw its first accelerator beam, and soon after, event displays showing tracks in the chambers and energy in the calorimeters became available. Since then, stable beam operation into Hall D has allowed the experiment to make great progress towards making its key performance parameters and demonstrating that the essentials of the experiment are functioning. For some of the physicists, the analysis of these data took precedence over eating turkey during the Thanksgiving weekend. And just last night, beam was sent to three halls – Halls A, B, and D – at the same time.
When we stand back and put the achievements of a complete year together, it is very impressive, but it also emphasizes what is left to be done. You will note that in this article I have often made use of the pronoun “we”; it's easier to write that way. Of course, it should really be “you”.
During the course of 2014, YOU have made substantial progress towards a 12 GeV physics program.